1. Field of the Invention
The present invention relates to an image processing apparatus in which the character processing works such as inputting, editing and the like of character string can be performed on a display screen.
2. Description of the Prior Art
Conventionally, character processing apparatus of the class described is generally equipped with a buffer memory for storing a display character string having memory areas each of which unconditionally corresponds to one display area on a display screen (or CRT) to the display character string, and a character at an arbitrary position on the CRT is stored in the buffer memory. In this way, since a buffer memory which corresponds to the CRT on a one-to-one-basis is used, for example, there is no need to input characters at and after a carriage return (CR). However, since it is necessary to display a blank on the CRT, a number of memory area portions are not used in the buffer memory. In addition, there is also a drawback such that a buffer memory having a large memory capacity is needed.
Therefore, a method has been proposed whereby the efficiency of the buffer memory is improved as the buffer memory having a continuous length is used as it is, without dividing the buffer memory into fixed lengths so that the buffer memory having a small memory capacity can be used. According to this method, the character string inputted is stored in the buffer memory as a continuous character string; thus, in the case where the above-mentioned CR is inputted a plurality of times, those plurality of CR codes may be memorized and all of the plurality of spaces may be merely stored. An amount of portions that are not used in the buffer memory becomes small and the buffer memory of a small capacity is enough.
That is, in the latter continuous use method, the space portion is replaced by a special code, thereby enabling the use efficiency of the buffer memory to be raised. However, in case of the latter method, with respect to a particular display function (e.g., tab or the like), it is necessary to also display the space portion which does not exist in the buffer memory. Consequently, in the latter continuous use method, it is impossible to easily perform the input and edit processings of new characters that could be easily performed at any positions on the CRT in the former buffer memory method of one-to-one correspondence. As described above, although the latter apparatus has been proposed to eliminate the drawback regarding the fixed length in the former conventional apparatus, this causes a new problem such that the input and edit processing works which can be easily carried out by the former apparatus cannot be easily executed by the latter apparatus.